In contrast to the autoprocessing of caspase-9, little is known about the biological significance of caspase-9 processing by caspase-3 via a feedback loop in vivo. We prepared antisera against mouse caspase-9 cleavage sites so that only the activated form of mouse caspase-9 was recognized. Using these antisera and caspase-9-and caspase-3-deficient mouse embryonic fibroblasts, we demonstrated that mouse caspase-9 is initially autoprocessed at D 353 and D 368 at low levels during staurosporine-induced apoptosis, whereupon the D 368 and D 168 sites are preferentially processed over D 353 by activated caspase-3 as part of a feedback amplification loop. Ac-DEVD-MCA (caspase-3-like) and Ac-LEHD-MCA (caspase-9-like) cleavage activities clearly showed that caspase-9 autoprocessing was necessary for the activation of caspase-3, whereas full activation of caspase-3 and caspase-9 was achieved only through the feedback amplification loop. This feedback amplification loop also played a predominant role during programmed cell death of dorsal root ganglia neurons at mouse embryonic day 11.5. Cell Death and Differentiation (2001) 8, 335 ± 344.

No abstract

A simple one-stage reaction system which yields 2-C hydroxymethylated aldopentose has been investigated. Four different 2-C branched aldopentoses (2-C hydroxymethylated d-arabinose, d-ribose (Hamamelose), l-lyxose, and d-xylose) were prepared from the corresponding ketoses (d-psicose, d-fructose, l-sorbose, and d-tagatose, respectively). These branched sugars were synthesized by a similar mechanism to the 2-C epimerization of aldose using a nickel complex. It was confirmed that the isomerization of ketose to the side-branched sugar proceeded in the ternary nickel complex through a sequence of stereospecific rearrangements in the sugar. The yields were dependent upon the structure of the substrate ketose and the nickel-ethylenediamine complex. N,N′-Dialkylated cyclohexanediamines were the most suitable ligands for preparing the 2-C hydroxymethylated branched chain sugar.

No abstract